1. Field of the Invention
The present invention relates to a display unit and a control method thereof, and, more particularly, to a display unit having a non-changeable memory and a changeable memory to separately store extended display identification (EDID) information by dividing the EDID information and a control method thereof.
2. Description of the Related Art
Extended display identification (EDID) information is information to identify a display unit and includes a variety of information required to identify the display unit.
For example, the EDID information may comprise display information such as an EDID header, a manufacturer identifying code, a product identifying code, a manufacturing date, a EDID structure version, a basic display variable and a property, a color property, timing information and a checksum byte to detect an error.
The EDID information is stored in an electrically erasable programmable read only memory (EEPROM) by a manufacturing process and is stored as one of analog data and digital data according to a video signal supplied from an external device.
When a user turns on the display unit, the EDID information stored in the EEPROM is read by a microcontroller unit and the EDID information stored in the EEPROM is tested for whether the EDID information has an error.
The error is determined by testing whether a result of an addition of the EDID bytes is equal to 0. That is, if the addition of the EDID bytes is equal to 0 without an overflow, an error is determined to have not occurred. A value of the checksum byte is previously set to make the result of the addition of the EDID bytes equal to 0 and the checksum byte is included in the EDID information to be stored.
Thus, if the result of the addition of the EDID bytes is equal to 0, the EDID information is determined to not have an error. Otherwise, the error is determined to have occurred in the EDID information or when the microcontroller unit reads the EDID information.
If the EDID information is determined to not have the error, the microcontroller unit of the display unit stores the EDID information stored in the EEPROM in a random access memory (RAM) to make the EDID information stored in the EEPROM accessible by an external device.
If a conventional computer is booted, an operating system (OS) of the computer reads out the EDID information from the RAM of the display unit through a plug and play (PnP) and installs a driver that is proper for the display unit.
For the PnP, a display data channel (DDC) that is proposed as a standard by video electronics standards association (VESA) is selected as a communication standard for a communication between the display unit and a computer main body. The DDC standard includes a DDC 1 standard supporting a one-way transmission and a DDC 2B standard, a DDC 2AB standard and a E-DDC standard supporting a two-way transmission, thereby enabling a communication between the computer main body and the display unit.
However, in the conventional computer, if an error occurs and incorrect EDID information is input in the computer main body, the display unit cannot display a picture. Moreover, a long time is required to store the EDID information in the EEPROM by the manufacturing process.